The most comprehensive notes in the history: explain the causes and prevention of color stains on polyester knitted fabrics

Abstract: polyester knitted fabric after dyeing high temperature and pressure, due to the large amount of oil during the weaving fabric, the fiber aggregate with the dye molecule to produce an oligomer, causing color stains, which seriously affect the quality of the product. In order to control the occurrence of this problem , the analysis, research and study of stains were carried out, specific methods for controlling problems were found, preventive measures were proposed, product quality was improved, and the company's economic benefits were increased.

1 Polyester knitted fabric

Belonging to the hydrophobic polyester fibers, lack binding group can react with the dye, a water-soluble dye can not only use a small molecular weight, non-ionic water-soluble strong group, a lower solubility of nonionic disperse dye . Polyester structure is tight , atmospheric pressure boiling dye , the dye is difficult to diffuse into the fiber inside the fiber dyed through, so the use of high temperature and high pressure dyeing.

2 Disperse dye staining

Disperse dyes are performed in a hot and humid state under high pressure. The dye is dispersed in the aqueous solution by a plurality of single crystal molecules in a granular state through a dispersant. The dyeing rate is slow within 100 DEG C. Even if the dyeing bath is dyed in a boiling dye bath, the dyeing rate and the dye uptake percentage are not so high. It must be pressurized below 2atm (2.02×10 5 Pa) and the bath temperature can be increased to 120-130°C. As the temperature increases, the segments of the fiber molecules move violently, and the instantaneous pores produced are also larger and larger. the diffusion also faster, increasing the rate of diffusion of the dye into the interior of the fiber, dyeing rate increases, until the dye is accomplished exhaustion dyeing.

Since the disperse dye has a low solubility in water, the dye in the dyeing liquid needs to be dispersed in the dye bath by a large amount of dispersant to dye the polyester fiber. In order to achieve a better dyeing effect. Usually need to add a certain amount of dyeing auxiliaries. The role of these dyeing auxiliaries in the dyeing process are: increase the solubility of disperse dyes, promote the adsorption of disperse dyes on the fiber surface, plasticize the fibers or increase the degree of swelling, and accelerate disperse dyes The diffusion rate in the fiber improves the dispersion stability of the dye.

The auxiliary agent used for high temperature and high pressure dyeing of polyester fiber in general contains a carrier for plasticizing the fiber , a dyeing agent for solubilizing the disperse dye or stabilizing the dye suspension, and the like, and has a very important role in the dyeing of the polyester fiber.

3 Types of stains

The color points are as follows:

3.1 Stains

Like the dyed color , deeper , and the same thing as the imprint , most of them have positive and negative sides , and sometimes there are dirty stains on the color stains that can get rid of . Such color spots and color stains account for more than 60% of the total . Most of them appear to be irregular , ranging in size from mung beans to soybeans , but they have large fingernails in severe cases.

3.2 Black spots

The main focus in brown, light brown, including color, light beige, coffee, dark brown, black small color dot size of sesame seeds, like black oil pen point on the cloth a bit the same.

3.3 The color point of the dyed color

It is darker than the color of the first case, and it is not large. Sometimes it can collapse. Generally, there are more two ends of a cylinder and less in the middle.

These three types can be found when dyeing the cylinder out of the cloth. There was a minor repair with tincture, and serious blackening.

3.4 Scattered color point

There is also a dark golden point, no cloth after drying by the dryer has a golden golden color point to point out when the black cloth, this type yellow spot with an alkali degreasers + may be removed. Especially when it is changed to black, it is more likely to appear and it is scattered on the cloth surface.

4 Causes of stain formation

4.1 The choice of additives

The emulsifying agent has poor emulsifying stability, and oily substances are precipitated at a high temperature, and the coloring of the dye condenses. The oil on the fabric is not treated cleanly, and the swelling agent is free to stain out when dyeing. It is recommended to add a high temperature dispersant.

4.2 Uneven material and defoamer generated at high temperatures generate oil

The dyestuff was not evenly mixed and was not directly fed into the dyeing machine; the grey cloth was foamed when the temperature in the dyeing tank reached 80°C, and the operation temperature of the antifoaming agent was too high.

4.3 Improper control of dyeing heating rate

Some dyes do not have good dispersibility, and dyeing temperature control is improper . If the dyeing agent is too fast , the dispersant or paraffinizer will not be able to withstand the high temperature, causing the dye to form secondary dyes to form dye spots. When the additives are added, some of them are required to be separately diluted (high in solid content). Produce suspension points that combine with dyes to form dye spots;

Some color dots are very small and point-like distribution and can only be found by careful observation, and are different from dye shades. That is because the dye itself contains insoluble matter caused in the manufacturing process of these dyes dispersion is destroyed can not enter the fiber interior. Most of these situations occur in light or brilliant colors;

The diffusion effect of red dyes may not be good and it needs to be added as a diffusing agent.

If the dyeing leveler is added with a leveling agent and no dispersant is added, then the dispersibility is insufficient, the dyes will gather, and the color point will be generated.

5 Prevention and treatment methods

5.1 Pre-processing

Pre-dye treatment is mainly to remove the commensal organisms from natural fibers . Of polyester and other synthetic fibers for which it is removed after adding artificial "impurities" spinning or weaving process comprises adding an oil and grease contamination, dust, pigments and the like. Among them , the most noteworthy is the oil agent . Lubricants contain lubricants, emulsifiers, antistatic agents, and the like. Applying oil to synthetic fibers such as polyester spinning, weaving is necessary.

Oil must be washed out during dyeing and finishing, if not washed before dyeing, with t

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